Frequency hopping is a method of transmitting signals by switching a carrier among many frequency channels, using a pseudorandom sequence known to both the transmitter and the receiver. Frequency hopping is commonly used to avoid jamming. For instance, a large frequency hopping set may be used so that communications can be carried out in the presence of a jammer. It is noted, however, that spectrum shortage is forcing the frequency hopping set to be smaller than what may be required for it to reliably mitigate jamming. Self-jamming, where friendly parties may use a frequency hopping set with overlapping frequencies, is also becoming common due to lack of available frequency channels.
It is also noted that conventional frequency hopping techniques do not have any mechanisms to react to jamming. A network implementing conventional frequency hopping, for example, merely follows a pre-determined pseudorandom hopping pattern that is used by all radio nodes in the network to remain in network synchronism.